Thymol Blue (5g)
Thymol blue (thymolsulfonephthalein) is a brownish-green or reddish-brown crystalline powder that is used as a pH indicator. It is insoluble in water but soluble in alcohol and dilute alkali solutions.
Thymol blue (pH indicator) | ||
below pH 8.0 | above pH 9.6 | |
8.0 | ⇌ | 9.6 |
Thymol blue (pH indicator) | ||
below pH 1.2 | above pH 2.8 | |
1.2 | ⇌ | 2.8 |
It transitions from red to yellow at pH 1.2–2.8 and from yellow to blue at pH 8.0–9.6. It is usually a component of Universal indicator.
At wavelength (378 – 382) nm, extinction coefficient > 8000 and at wavelength (298 – 302) nm , the extinction coefficient > 12000.
Structures
Thymol blue has different structures at different pH.